JPH0583161B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a solenoid drive circuit for driving a solenoid, which is a load having an inductance component.

<Prior art> As shown in Fig. 3, a conventional solenoid drive circuit has a drain D connected to the power supply side between the power supply _VB and the solenoid 1, and a source S connected to the solenoid side.
A field-effect transistor (FET) 2 in the driving stage is connected to the circuit, and the input voltage V _IN to the gate G of this field-effect transistor 2 is controlled to turn on/off the solenoid 1. There is. Note that 3 in the figure is a charge pump circuit for boosting the input voltage V _IN .

That is, when the input voltage V _IN rises and the gate G voltage of the field effect transistor 2 becomes H level, the field effect transistor 2 turns on and the solenoid 1 is driven by the current I _L , and the input voltage increases.
When V _IN falls and the gate G voltage of the field effect transistor 2 becomes L level, the field effect transistor 2 is turned off and the driving of the solenoid 1 is stopped (see FIG. 4).

<Problem to be solved by the invention> However, when driving the solenoid 1,
Since it has an inductance component, during the on/off control, the energy stored in the inductance is transferred to the field effect transistor 2.
As a result, the solenoid 1 takes a long time to turn off, and there is a problem in that fast control is not possible, especially in duty control.

That is, the gate G of the field effect transistor 2
When the voltage reaches the L level (0V), the field effect transistor 2 is turned off, but in the case of the solenoid 1 having an inductance component, current continues to flow due to energy discharge. Therefore, the source S voltage takes a negative value and becomes lower than the gate G voltage, turning the field effect transistor 2 on and performing inductance discharge. Therefore, the field effect transistor 2 remains in an ON state intermittently until the potential difference between the gate G and the source S becomes equal to or less than the predetermined voltage _VTH . In FIG. 4, A indicates the valve opening current level in the case of valve drive, and B indicates the valve closing current level.

SUMMARY OF THE INVENTION In view of these conventional problems, it is an object of the present invention to provide a solenoid drive circuit that can effectively control on/off of a solenoid.

<Means for Solving the Problems> For this reason, the present invention interposes a drive stage field effect transistor with the source connected to the solenoid side between the power supply and the solenoid, and connects the field effect transistor to the gate of the field effect transistor. In a solenoid drive circuit that controls input voltage to turn on and off a solenoid, the gate and source of the field effect transistor in the drive stage are connected via another field effect transistor, and the gate and source of the field effect transistor in the drive stage are connected via another field effect transistor. A predetermined voltage source is connected to the drive stage, and a constant voltage diode is interposed between the drain and source of the field effect transistor of the drive stage.

<Function> In the above configuration, when the input voltage falls and the gate voltage of the field effect transistor in the drive stage becomes L level (0V), the field effect transistor turns OFF, but the solenoid has an inductance component. Therefore, it tries to keep the current flowing. As a result, the source voltage becomes a negative value,
A potential difference is generated between the gate and source of a field effect transistor, but since a predetermined voltage source is connected to the gate of another field effect transistor, the potential difference between that gate and source is larger, and this other field effect transistor Since the effect transistor turns on first, a small current flows in and keeps the gate and source of the drive stage field effect transistor at the same potential, so the drive stage field effect transistor does not turn on. The solenoid then performs inductance discharge via the constant voltage diode. This results in
It is possible to hasten the transition of the solenoid to the OFF state.

<Example> An example of the present invention will be described below based on FIGS. 1 and 2.

Referring to Figure 1, the drain D is connected to the power supply side between the power supply V _B (=12V) and the solenoid 1, the source S is connected to the solenoid side, and a field effect transistor (hereinafter referred to as FET) 2 of the drive stage is connected. By controlling the input voltage V _IN applied to the gate G of the FET 2 via the charge pump circuit 3, the solenoid 1 is turned on and off as shown in FIG.

Here, the gate G and source S of FET2
This other FET is connected through another FET4.
A predetermined voltage source (V ₁ ) 5 is connected to the gate G of 4. If the operating voltage (gate-source voltage) of FETs 2 and 4 is V _TH =1.5V, then V ₁ is approximately 0.8V.

Further, a constant voltage diode 6 is interposed between the drain D and the source S of the FET 2.

Next, the action will be explained.

When the input voltage V _IN rises, the gate G of FET2
When the voltage reaches H level, the FET 2 is turned on and the solenoid 1 is driven.

When the input voltage V _IN falls, the gate G of FET2
When the voltage reaches the L level, FET 2 turns off, but in the case of solenoid 1, which has an inductance component, current continues to flow due to energy discharge. At this time, the source S voltage becomes a negative value, creating a potential difference between the gate G and source S of FET2, but since the predetermined voltage source 5 is connected to the gate G of another FET4, that gate G
The potential difference between source S is larger, and this other
Since FET4 turns on first, a small current flows into the source S side of FET2 through FET4,
Since the gate G and source S of FET2 are kept at the same potential, FET2 will not turn on. On the other hand, the constant voltage diode 6 operates, and the solenoid 1 performs inductance discharge via the constant voltage diode 6. This can speed up the shutoff.

<Effects of the Invention> As described above, according to the present invention, when controlling the on/off of a solenoid, it is possible to turn off the solenoid earlier and improve controllability.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a circuit diagram showing a conventional example, and FIG. 4 is a diagram showing operating characteristics same as the above. 1...Solenoid, 2...Drive stage field effect transistor (FET), 3...Charge pump circuit, 4...Field effect transistor (FET), 5...
...Voltage source, 6... Constant voltage diode.

Claims (1)

[Claims] 1 Solenoid drive in which the source is connected to the solenoid side between the power supply and the solenoid, a field effect transistor is inserted in the drive stage, and the input voltage to the gate of this field effect transistor is controlled to turn on and off the solenoid. In the circuit, the gate and source of the field effect transistor of the drive stage are connected via another field effect transistor, and a predetermined voltage source is connected to the gate of this another field effect transistor, while the electric field of the drive stage is A solenoid drive circuit characterized by interposing a constant voltage diode between the drain and source of an effect transistor.